3D Resources Limited expects to commence a 2000 metre reverse circulation drilling program at the Adelong Gold Project in the second quarter of 2021, to test the deeper parts of the Challenger orebody to refine and finalise mine plans before mining commences.
The Adelong Gold Project covers 70 square kilometres and comprises the old Adelong Goldfield in Southern NSW, located approximately 20 kilometres from Tumut and 80 kilometres from Gundagai.
The project carries an existing JORC Resource of 180,600 ounces of gold and 17 freehold properties with all mining and processing plant equipment on-site, and until recently was a producing mine.
The proposed drilling program at the mine, which is ready to commence, has been slightly delayed due to the recent NSW floods which have impacted the availability of drillers. The company does not expect the delays in commencement of the drilling program to exceed one month and will provide further updates in due course including results as they are received.
Nine of the proposed ten holes are designed to test areas around the periphery of the open cut to infill some of the existing drilling information which would allow the pit plan to be optimised and improve the understanding of the transition to underground mining.
The remaining hole to be drilled is within the planned open cut and aims to provide additional data on the nature of the waste rock likely to be generated from mining operations to ensure there is no potential for pollution.
The selected plant design for the mine involves a major upgrade in the plant’s capacity to provide some economies of scale and initially the plan is to operate this on a 12 hour per day basis that will allow the plant to scale up as additional resources are brought into production.
At a planned throughput of approximately 35 tonnes per hour, the operating costs are estimated to be around $40/tonne of ore.
The use of gravity as the main recovery method at a coarse grind size has also allowed the company to target stacking of tailings as a way to manage waste from the operation. The sand tailings may be sold as they contain no chemical additives. Only the slimes/fines which are likely to go to the flotation circuit would require disposal in a tailings facility.
The company is evaluating both open cut and underground mining options for the Challenger Mine. An initial open cut mine plan has been adopted and designed with a two stage cut back and aims to extract sufficient ore for the first three years of operation of the current plant.
The complete pit design has an overall stripping ratio of 11:1. This would then allow access from the open cut for underground development to extract any additional commercial resources.
Various contract miners were approached to assess the costs of open cut mining and indicative quotes have been received. In addition, the Company engaged MiningOne to prepare plans for underground mining options and their report is expected shortly.
A bulk sample of Adelong Ore taken from the run of mine (ROM) stockpiles was sent to Mineral Technologies for testing using spirals. The tests have shown that spirals can recover between 80-85 per cent of the gold in a high-grade concentrate with a concentrate grade of more than 100 grams per tonne of gold. This supports the idea that the vast majority of the gold can be recovered by low-cost gravity processes.
Samples of the slimes/fines (mainly less than 20 microns) generated from the grinding of this sample have now been sent for flotation testing. Initial sighter tests showed a recovery of 73 per cent of the gold in a rougher concentrate.
A further sample of the tailings from the spiral test work that graded less than 0.4 grams per tonne of gold was sent for further testing to prove up the plant design which includes the Knelson concentrator (currently installed in Adelong) as a scavenger circuit to recover much of the gold lost to tailings.
Another short term program of metallurgical testing on 20kg samples is planned to compare the Adelong Ore with samples of ore from different potential mine sites, to confirm the plant design selected will be equally successful in treating ore from these mines.